#include <stdio.h>

int main()
{
	int month = 0;
	printf("请输入一个月份:");
	scanf("%d",&month);
	switch(month)
	{
		case 1:
		case 3:
		case 5:
		case 7:
		case 8:
		case 10:
		case 12:
			printf("31"); break;
		case 2:
			printf("28"); break;
		default:
			printf("30"); break;
	}
}
